1. Topic: Polyatomic Ions Do Now: p.12

2. Potassium (K) and Fluorine (F) Zinc (Zn) and Iodine (I) Sodium (Na) and Oxygen (O) Magnesium (Mg) and Oxygen (O) Aluminum (Al) and Oxygen (O) Calcium (Ca) and Bromine (Br) Cesium (Cs) and Iodine (I) Silver (Ag) and Sulfur (S) KF Na 2 O MgO Al 2 O 3 CaBr 2 CsI ZnI 2 Ag 2 S Review Binary – look up oxidation numbers and Criss-Cross

3. Same Idea works if compound contains a polyatomic ion Look up oxidation numbers then Criss-Cross Hint: Put parenthesis around polyatomic ion Al(SCN) 3

4. Formulas with polyatomics What’s the formula for the compound formed from Al and SCN? Al +3 (SCN) -1 The charges must add up to zero, so write the symbols, positive first! Al(SCN) 3

5. Try a few more: Na +1 and (OH) -1 K +1 and (HCO 3 ) -1 Mg +2 and (CO 3 ) -2 Li +1 and (NO 3 ) -1 Ca +2 and (SO 4 ) -2 Na(OH) = NaOH K(HCO 3 ) = KHCO 3 Mg 2 (CO 3 ) 2 = MgCO 3 Li(NO 3 ) = LiNO 3 Ca 2 (SO 4 ) 2 = CaSO 4

6. These are more challenging: Mg +2 and (PO 4 ) -3 Al +3 and (NO 3 ) -1 Fe +2 and OH -1 Hg 2 +2 and SCN -1 Mg +2 and HCO 3 - Al +3 and C 2 O 4 2- Mg 3 (PO 4 ) 2 Al(NO 3 ) 3 Fe(OH) 2 Hg 2 (SCN) 2 Mg(HCO 3 ) 2 Al 2 (C 2 O 4 ) 3

7. Some of the most challenging are Zinc + Nitrate ion Magnesium + Hydroxide ion Lithium + Carbonate ion Potassium + Sulfate ion Calcium + Phosphate ion Beryllium + Chlorate ion Zn(NO 3 ) 2 Mg(OH) 2 Li 2 CO 3 K 2 SO 4 Ca 3 (PO 4 ) 2 Be (ClO 3 ) 2